Approaches for Extracting Nanofibrillated Cellulose from Oat Bran and Its Emulsion Capacity and Stability

The pretreatment process is an essential step for nanofibrillated cellulose production as it enhances size reduction efficiency, reduces production cost, and decreases energy consumption. In this study, nanofibrillated cellulose (NFC) was prepared using various pretreatment processes, either chemical (i.e., acid, basic, and bleach) or hydrothermal (i.e., microwave and autoclave), followed by disintegration using high pressure homogenization from oat bran fibers. The obtained NFC were used as an emulsifier to prepare 10% oil-in-water emulsions. The emulsion containing chemically pretreated NFC exhibited the smallest oil droplet diameter (d32) at 3.76 μm, while those containing NFC using other pretreatments exhibited d32 values > 5 μm. The colors of the emulsions were mainly influenced by oil droplet size rather than the color of the fiber itself. Both NFC suspensions and NFC emulsions showed a storage modulus (G′) higher than the loss modulus (G″) without crossing over, indicating gel-like behavior. For emulsion stability, microwave pretreatment effectively minimized gravitational separation, and the creaming indices of all NFC-emulsions were lower than 6% for the entire storage period. In conclusion, chemical pretreatment was an effective method for nanofiber extraction with good emulsion capacity. However, the microwave with bleaching pretreatment was an alternative method for extracting nanofibers and needs further study to improve the efficiency.

Energy and exergy analysis of a downstream single-row air washer at different droplet diameters for air cooling application

This study proposes a downstream single-row air washer for air cooling. The theoretical energy and exergy balance models were established at different droplet diameters and verified by the experimental data. Based on the abovementioned theoretical relationship, the single performance indicator of heat exchange efficiency (HEE) and exergy efficiency was quantitatively analyzed; a comprehensive analysis method of two indicators was proposed, combining HEE and exergy efficiency, and a numerical simulation was carried out. Results show that the smaller the droplet diameter and the larger the water–air ratio, the lower the dry-bulb temperature of the outlet air and the higher the HEE and exergy flux destruction. When the droplet diameter is less than 440 μm, the droplet diameter does not affect exergy efficiency and dry-bulb temperature. When the droplet diameter is larger than 440 μm, the droplet diameter is positively correlated with the air outlet dry-bulb temperature and exergy efficiency; in contrast, the water–gas ratio is negatively correlated with the air outlet dry-bulb temperature. An engineering case reveals that when the air outlet temperature is less than 34°C, the critical water–gas ratio can be set as 2.6 (mass ratio). At this time, the HEE is more than 90%, the exergy efficiency is more than 60%, and the critical value of droplet diameter is 440 μm. The research results provide an essential theoretical basis for the optimization of engineering design calculation.

Liquid Droplet Impact Over Hydrophobic Mesh Surfaces and Assessment of Weber Number Dependent Characteristics

Impacting droplets and droplet ejection from hydrophobic mesh surfaces have interest in biomedicine, heat transfer engineering, and self-cleaning of surfaces. The rate and the size of newborn droplets can vary depending on, the droplet fluid properties, Weber number, mesh geometry, and surface wetting states. In the present study, impacting water droplets onto hydrophobic mesh surface is investigated and impact properties including, spreading, rebounding, and droplet fluid penetration and ejection rates are examined. Droplet behavior is assessed using high recording facilities and predicted in line with the experiments. The findings reveal that the critical Weber number for droplet fluid penetrating/ejecting from mesh screen mainly depends on the droplet fluid capillary length, and hydrophobic mesh size. The contact time of impacting droplet over mesh surface reduces with increasing droplet Weber number, which opposes the case observed for impacting droplets over flat hydrophobic surfaces. The restitution coefficient attains lower values for impacting droplets over mesh surfaces than that of flat surfaces. The rate and diameter of the ejected droplet from the mesh increases as droplet Weber increases. At the onset of impact, streamline curvature is formed inside droplet fluid, which creates a stagnation zone with radially varying pressure at the droplet fluid mesh interface. This reduces the ejected droplet diameter from mesh cells as mesh cells are located away from the impacting vertical axis.

Current Perspectives on Nanoemulsions in Targeted Drug Delivery

Nanoemulsions are an isotropical mixture of oil, surfactant, and water with droplet diameter approximately in the range of 10-100 nm. They are being exponentially used for drug delivery systems for the influential administration of therapeutical agents because of their potential advantages over other approaches. Nanoemulsions can be used to design delivery systems that have increased drug loading, enhanced drug solubility, increased bioavailability, controlled drug release, and enhanced protection against chemical or enzymatic degradation. Moreover, nanoemulsions have better thermodynamical stability to flocculation, sedimentation, and creaming than conventional emulsions. Their small droplet dimensions and large droplet surface area positively influence drug transport and delivery, along with allowing targeting to specific sites. This chapter focuses on recent applications of nanoemulsions in the area of drug delivery.

Effect of Corrosion and Wall Textures on Wettability and Heat Flux at Non-Isothermal Conditions

The corrosion behavior, evaporation and heat transfer of aluminum alloy during droplet evaporation of an aggressive solution of NaCl and hydrogen peroxide in water have been studied experimentally. To date, the effect of corrosion on the evaporation and heat transfer of droplet salt solutions on textured surfaces remains insufficiently explored. The corrosion resistance of the material and the contact angle increase with an increase in the number of laser penetrations after laser texturing. Studies conducted using an electron microscope and Energy-Dispersive X-ray Spectroscopy (EDS) mapping show that the maximum amount of adsorbed hydrocarbon impurities falls on areas with a large number of pits. In the process of metal corrosion, wettability and heat transfer change. In spite of the fact that laser exposure significantly increases the corrosion resistance, the wettability of the wall changes significantly due to corrosion. The wetted diameter of a droplet changes over time, which leads to an increase in the evaporation rate and heat flux. The heat flux during evaporation of a droplet on a heated wall depends on the water droplet diameter, the texture of the wall and the corrosion resistance.

Physical, morphological and storage stability of Clove oil nanoemulsion based delivery system

Clove oil based Nanoemulsions (NE) were prepared ultrasonically using Tween 80 and soy lecithin as synthetic and natural surfactants, respectively. The developed NEs were characterized for various parameters (particle size, polydispersity index, zeta potential, morphology, viscosity, colour, turbidity and pH) and the comparative effect of both the surfactants at variable levels (oil:tween 80-1:1, 1:2, 1:3 and 1:4 and oil: soy lecithin- 1:1, 1:1.5 and 1:2) was assessed. It was found that the type of surfactant and oil to surfactant ratio significantly affected particle size and stability of NEs. The NE prepared using tween 80 @1:3 had smallest average droplet diameter (40.9 nm). The formulated NEs were stored at 25 °C and 4 °C and analyzed for turbidity, pH and phase separation up to 90 days. Results revealed that the type and concentration of the surfactant significantly influenced the particle size and stability of NEs. NEs prepared using tween 80 were found to be more viscous than those prepared with soy lecithin. The prepared clove oil NEs have important implication to be used as a natural delivery system to increase the shelf life of food products.

Nanoemulsions containing Garcinia mangostana L. pericarp extract for topical applications: Development, characterization, and in vitro percutaneous penetration assay

A highly stable oil-in-water nanoemulsion for topical applications, containing mangostins extracted from the pericarp of mangosteen (Garcinia mangostana L.), is a promising strategy to protect mangostins as well as to improve penetration of these important antioxidants through the skins. Nanoemulsions consisted of virgin coconut oil as the oil phase, Tween-80 and Span-80 as surfactants, and xanthan gum as the thickening agent, were prepared using the high-energy and low-energy emulsification methods. The nanoemulsions that were stable up to 28 days had oil droplet diameter of 220 nm to 353 nm and zeta potential of -46.9 mV to -63.7 mV. The accelerated stability test showed that the most stable nanoemulsions were those prepared using the low-energy emulsification method with an estimated shelf life of eleven months, composed of 11% oil phase, 17% surfactant, and 72% aqueous phase. The in vitro percutaneous penetration test for the nanoemulsion with added xanthan gum provided high cumulative skin penetration of mangostins of up to 114 μg/cm2. The results of this study indicate that virgin coconut oil-based nanoemulsions containing mangostins, prepared using the low-energy emulsification method, stabilized by xanthan gum and mixed at 40°C can prospectively be used for topical applications.

Numerical Study of Evaporation Modelling for Different Fuels at High Operating Conditions in a Diesel Engine

A fuel injection system in a diesel engine has different processes that affect the complete burning of the fuel in the combustion chamber. These include the primary and secondary breakups of liquid fuel droplets and evaporation. In the present paper, evaporation of two different diesel fuels has been modelled numerically. Evaporation of n-heptane and n-decane is governed by the conservation equations of mass, energy, momentum, and species transport. Results have been plotted by varying the droplet diameter and temperature. It was observed that droplet size, temperature of droplets, and ambient temperature have notable effect on the evaporation time of diesel fuel droplets in the engine cylinder.

On-demand Ferrofluid Droplet Formation With Non-linear Magnetic Permeability in the Presence of a Non-uniform Magnetic Field

The magnetic actuation of ferrofluid droplets offers an inspiring tool in widespread engineering and biological applications. In this study, the dynamics of ferrofluid droplet generation with a Drop-on-Demand feature under a non-uniform magnetic field is investigated by multiscale numerical modeling. Langevin equation is assumed for ferrofluid magnetic susceptibility due to the strong applied magnetic field. Large and small computational domains are considered. In the larger domain, the magnetic field is obtained by solving Maxwell equations. In the smaller domain, a coupling of continuity, Navier Stokes, two-phase flow, and Maxwell equations are solved by utilizing the magnetic field achieved by the larger domain for the boundary condition. The Finite volume method and coupling of level-set and Volume of Fluid methods are used for solving equations. The droplet formation is simulated in a two-dimensional axisymmetric domain. The method of solving fluid and magnetic equations is validated using a benchmark. Then, ferrofluid droplet formation is investigated experimentally and the numerical results are in good agreement with the experimental data. The effect of 12 dimensionless parameters including the ratio of magnetic, gravitational, and surface tension forces, the ratio of the nozzle and magnetic coil dimensions, and ferrofluid to continuous-phase properties ratios are studied. The results showed that by increasing the magnetic Bond number, gravitational Bond number, Ohnesorge number, dimensionless saturation magnetization, initial magnetic susceptibility of ferrofluid, the generated droplet diameter reduces, whereas the formation frequency increases. The same results were observed when decreasing the ferrite core diameter to outer nozzle diameter, density, and viscosity ratios.

CFD MODEL TO ANALYZE SO2 ABSORPTION IN A SEAWATER DROPLET

In the recent years, seawater scrubbers have become an interesting option to reduce SO2 emissions in marine engines. In this regard, this paper proposes a numerical model to analyze SO2 absorption in seawater. A single seawater droplet was analyzed, and the developed model was used to predict the influence of several parameters on the desulphurization efficiency, such as the droplet diameter, SO2 concentration, alkalinity and temperature. It was found that a droplet of 200 μm initial diameter can absorb up to 1.77∙10-14 mol of S for the parameters analyzed, and this reduction improves when the alkalinity and SO2 concentration are increased and diameter, seawater temperature and gas temperature are reduced. Differences up to of 21.5%, 19.8%, 2.2% and 16.3% in the S reduction were obtaining varying the SO2 initial concentration, alkaline initial concentration, initial liquid temperature and initial gas temperature respectively.